\w - represents the character class [A-Za-z0-9_] Character class
Despite this, I find it difficult to grasp how it is interpreted within a character class.
When I use
[\w-~]
let test = (str) => /^[\w-~]+$/.test(str)
console.log(test("T|"))it fails for T|
However, if I use
[A-Za-z0-9_-~]
let test = (str) => /^[A-Za-z0-9_-~]+$/.test(str)
console.log(test("T|"))it returns true,
I am puzzled by how these two expressions differ from each other?
In my perspective, the primary distinction between your two instances lies in the positioning of the hyphen character. What transpires is as follows:
let check = (str) => /^[A-Za-z0-9_-~]+$/.test(str)
console.log(check("T|"))
Here, it's construed as a range:
let check = (str) => /^[_-~]+$/.test(str)
console.log(check("|"))
This will result in true.
On the other hand:
let check = (str) => /^[\w-~]+$/.test(str)
console.log(check("T|"))
Due to \w representing a set of characters on its own, it interprets the hyphen character independently.
The placement of the hyphen and its neighboring elements can greatly alter its interpretation.
To prevent such predicaments, you can reposition it at the end like this:
let check = (str) => /^[A-Za-z0-9_~-]+$/.test(str)
console.log(check("T|"))
This will yield a result of false.
It appears that the key factor here is the range being used, specifically when utilizing the expression ^[A-Za-z0-9_-~]+$
The characters _-~ represent a range between _ (index 95) and ~ (index 126) in terms of ASCII values (case sensitive). This explains why T| is matched and returns true. However, if you were to use ^[\w-~]+$, it does not establish a specific range like _-~, causing it to fail and return false.
Similarly, ^[A-Za-z0-9-~]+$ also results in false because it lacks the inclusion of the _ character necessary for creating the _-~ range between _ (index 95) and ~ (index 126).
let test = (str) => /^[A-Za-z0-9-~]+$/.test(str)
console.log(test("T|"))For further clarification, refer to https://regex101.com/r/vbLN9L/5 in the EXPLANATION section.
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